This invention relates to an improvement in spark plugs and more particularly concerns a novel construction of the electrodes resulting in a longer, as well as a greater extent of the bodies of both electrodes at the gap location. The construction enables better maintenance and increased life of a set gap and enhances maintaining a constant temperature all along the gap. Making the ground electrode longer than those generally found in previously known spark plugs, and also constructing the ground electrode with a substantial body surface area, enables that electrode, particularly at the gap location, to be maintained at a high and constant temperature causing a more even ionization of the gases which results in more complete and cleaner efficient burning of the combustion fuel. The present invention eliminates problems, such as the insulator becoming heavily coated with oxides when the plug itself runs too hot, rapid wearing of the ground electrode by burning away of the firing area, and heavy deposits of carbon caused by cool points. The present electrode configuration by maintaining large gapping surface along a "sharp" area with a constant high temperature right at the gapping area avoids the foregoing problems when a plug insulator is too hot or the points are too cool.
There are many developments found in the prior art wherein attempts have been made to solve the foregoing problems. However, none of the art, insofar as applicant is aware, uses the idea of a hot/sharp edge relationship between the ground and central electrodes as well as incorporating an increased total length of the ground electrode by providing a specialized strip form configuration of that ground electrode bent or made with appropriate bend into a spiral form or arched shape with the terminal end gap portion of the ground electrode bent back toward the main body of the spark plug. Prior art known to applicant and which disclose special configurations of electrodes are seen in the following U.S. Pat. Nos. 1,087,897 to C. E. Talbert, dated Feb. 17, 1914; 1,364,262 to A. J. Faber, dated Jan. 4, 1921; 1,495,499 to J. Stanislawski, dated May 27, 1924; 2,060,340 to M. O'Marra, dated Nov. 10, 1936; 2,294,248 to J. J. Smulski, dated Aug. 25, 1942; 2,487,535 to to J. J. Fernandez, dated Nov. 8, 1949; 2,324,330 to H. R. Schnabel, dated June 6, 1967; 4,029,986 to J. H. Lara et al, dated June 14, 1977.
As evidenced by the above noted prior art patents many previously known spark plugs have proposed curved or spiral shapes on the ground electrode. None have a grounded electrode with a shape, body and relationship to the center electrode as is proposed by this present invention. The A. J. Faber patent does disclose a ground electrode which at first blush appears close to applicant's invention but it teaches that the ground electrode is a very small round wire coiled around the insulator with its end bent to first parallel the center electrode, then passing into a 3/4 circular portion coaxial with and spaced from the center electrode, then bent back toward the insulator, paralleling and spaced from the center electrode the same gap as the spacing of the 3/4 circular portion. The small wire lacks the rigid substantial body material and the provision of the flat strip terminal end portion of applicant's ground electrode that results in the beneficial hot/sharp sparking portion.